But this will only work if you uninstall vala-0.2x before.
Alternatively, you could try changing the ebuild so that wingpanel looks for vala-0.20; I'm not sure if you mean by "verified the ebuild" that you looked at it or that you already tried and changed it._________________Kali Ma
Now it's autumn of the aeons
Dance with your sword
Now it's time for the harvest